@article{MS2_1975__36_166395,
     author = {Herbert Busemann},
     title = {Planes with analogues to {Euclidean} angular bisectors.},
     journal = {Mathematica Scandinavica},
     pages = {5--12},
     year = {1975},
     volume = {36},
     zbl = {0299.50002},
     url = {http://geodesic.mathdoc.fr/item/MS2_1975__36_166395/}
}